1. Field of the Invention
This invention relates to an electrically operated, by means of a battery, power assist apparatus for a bicycle and more particularly, to a new and novel construction of that power assist apparatus for a bicycle.
2. Description of the Prior Art
Electric powered bicycles have long been known. All electric powered bicycles incorporate an electric motor which is powered by a battery. One way the bicycle is powered is by a motor that operates through a drive wheel which frictionally engages with a support wheel of the bicycle. Movement of the drive wheel adds power to the manual movement of the bicycle or could be the only source of movement of the bicycle. Frictional engagement between the drive wheel and a support wheel is only one method. Others involve many configurations of direct drive involving shafts, chains, and gears but with the common feature of the driving motor being mounted on the bicycle frame in one position or another (e.g., near the pedaling sprocket, on one of the stays or on a rack above the rear support wheel).
The prior art direct drive power assist devices for a bicycle have generally required complex gearing arrangements. Upon removal of the wheel for maintenance, such as tire repair, precise reengagement is difficult leading to excessive wear and noise during operation. Also, complex gearing arrangements are difficult to maintain in precise alignment when the bicycle encounters road bumps and holes. Also, incorporation of prior art power assist apparatuses on bicycles has made it difficult to remove and replace the wheel(s) of the bicycle for tire repair and/or replacement. Additionally, if it is desired to use the bicycle as a normal bicycle and have the bicycle not carry the extra weight of a battery pack plus a motor assembly, the prior art direct drive power assist apparatuses for bicycles have not been designed to be readily removable from the bicycle to permit normal manual usage without the extra weight involved.
In prior art direct drive systems, the motor is mounted on the bicycle frame. Therefore, when the wheel is removed and replaced on the frame, such as required in order to change a tire or to do other types of maintenance, slight variations prevent precise realignment between the drive gear of the motor and the drive gear mounted on the wheel. These slight variations often result in excessive noise and wear.